Cookware with a stick resistant surface is used daily by millions of households worldwide. Desirable characteristics in a stick resistant coating of cookware include good food release properties without affecting the taste of food, thermal stability at temperatures as high as 700° F., strong bonding with the substrate, environment compatibility and economic feasibility.
There are several stick resistant surfaces currently in use.
For example, DuPont produces an organic surface TEFLON® with excellent food release properties. Typically, a TEFLON® coating is applied to aluminum cookware. The aluminum provides for excellent heat conductivity while the TEFLON® provides excellent food release properties. However, TEFLON®-based stick resistant surfaces are soft and easy to scratch. A metal utensil, if used against a TEFLON®-coated surface, leaves a scar. Some cleaning utensils also leave scratches. While attempts have been made to provide TEFLON®-based stick resistant surfaces with increased scratch resistance, i.e. Calphalon One, such surfaces are still susceptible to scratching. Once the TEFLON®-based stick resistant surface is scratched, the stick resistant properties of the surface deteriorate. Further, and more importantly, TEFLON® begins to be released to the surrounding environment and into the human body. Recently, several research groups have shown that some chemicals used in making TEFLON® represent a health hazard. In particular, perfluorooctanoic acid (PFOA), a chemical used to make TEFLON®, has been detected in people as well as animals worldwide. PFOA has been detected in river otters in Oregon, polar bears in the Canadian Arctic, and in the blood of 96 percent of children tested in 23 states (Philadelphia Inquirer, Sep. 19, 2004). According to the U.S. Environmental Protection Agency, this chemical used to produce the stick resistant coating on pots and pans is hazardous to children and women of childbearing age, according to the U.S. Environmental Protection Agency (see EPA with the extension .gov of the world wide web). Further, cooking with TEFLON® has been reported to make a person sick with a temporary flu if a stick resistant pan gets overheated (see ewg with the extension .org of the world wide web). Birds have also been reportedly killed in houses where TEFLON® coated cookware was used (see ewg with the extension .org of the world wide web).
A hard anodized aluminum cookware is produced by Calphalon. Anodizing is a process by which a layer of extremely hard, but porous, aluminum oxide is applied to the surface of aluminum. This layer protects food from bare aluminum and helps protect the surface from wear. While marketed as a stick resistant coating, in reality use of a considerable amount of cooking oil and/or fat is required for food not to stick to this cookware. Further, at microscale levels, this layer is sponge-like in structure and can not be placed in the dishwasher because dishwashing detergent attaches to the layer causing permanent stains and deterioration of the integrity of the layer.
Recently, to over come the poor food release properties and the sponge-like structure, Calphalon released a new product, Calphalon One. In this product, the aluminum is anodized and the sponge-like layer is filled with TEFLON®. However, the presence of TEFLON® in this product represents the same concerns discussed above. Further, this newer product is still not dishwasher safe.
Scanpan is a Danish manufacturer specializing in durable cookware produced using different materials solutions as well as different surface coating techniques. Their cookware line consists of a combination of aluminum and titanium to provide a durable cookware. Recently they introduced a surface coating that combines the durability of ceramics and the excellent stick resistant properties of TEFLON® (Danish Patent DK989199T). However, while this surface is more scratch resistance because of the innovative ceramic coating, the use of TEFLON® as the final layer to provide stick resistant properties is still a concern.
Published U.S. patent application Ser. No. 2003/0022027 discloses a stick resistant cook surface comprising a substrate metal selected from stainless steel, carbon steel or titanium with a layer of ceramic nitride applied to the substrate metal.
Cast iron has a natural excellent food release properties due to its chemistry and microstructure. Further, it is thermally stable and can be used with metal utensils. However, cast iron cookware is extremely heavy requiring a strong arm to handle a 12 inch cast iron skillet. Cast iron cookware also rusts easily if not kept very dry all the time.
Thus, there is a need for an environmentally friendly stick resistant coating for cookware, cutlery and other cooking utensils.
A ternary ceramic material comprising Mn+1AXn (n=1,2,3) wherein M is a metal selected from the groups IIIB, IVB, VB, VIB and VIII of the periodic table of elements and/or their mixture; wherein A is selected from the groups IIIA, IVA, VA and VIA of the periodic table of elements and/or their mixture, and wherein X is carbon and/or nitrogen is described in U.S. Pat. No. 5,882,561, U.S. Pat. No. 5,942,455 and U.S. Pat. No. 6,461,989.
Use of this ternary ceramic material to produce slip-casted article formers such as latex gloves and condoms is described in WO 03/051791. Use of this ternary ceramic material in handling molten metals is described in DE60013322D. Use of this ternary ceramic material in resistance heating elements is described in AU774202.